So you can locate R3load in this directory I:\usr\sap\MP4\DVEBMGS20\exe?
Is there any logs in this log file R3load.log.1?
Did you try running the command directly? I would start by getting below command to work first, then try to narrow down the issue.
I:\usr\sap\MP4\DVEBMGS20\exe\r3load -testconnect -l R3load.log.test
